The instant invention relates generally to voltaic and electrochemical cells and more particularly to a cell using a lithium-aluminum alloy anode and an aqueous electrolyte.
Lithium and other light metals of groups IA and IIA of the periodic table are attractive candidates for voltaic cell anodes because of their light weight and high position in the electrochemical series. The prior art shows many cells involving such light metals and also alloys of aluminum and lithium. However the cells using a lithium-aluminum alloy anode conventionally use fused salt or other non-aqueous electrolytes including the alkali metal halides, alkaline earth metal halides, and molten electrolytes based on aluminum chloride.
Electrochemical cells based on the use of lithium or aluminum anodes and an aqueous electrolyte have been proposed, but have not been successful. One important consideration is the energy-volume ratio of the cell system. Theoretically a lithium system would produce 130 kw-hr/ft.sup. 3, and an aluminum system would produce 520 kw-hr/ft.sub. 3. However, an aluminum anode is relatively inactive in pH-neutral water at room temperature so the power could not be achieved. The lithium anode is too reactive with aqueous electrolytes and may be too uncontrollable for use in a cell.
The use of oxygen instead of water as the oxidant electrolyte in these aluminum or lithium anode fuel cells yields a higher output potential and energy. However in portable applications, the portage of oxygen and its containment vessels results in lesser power-to-weight and volume ratios than is obtainable from a system using available water as an electrolyte.